The present invention relates to a component mounting method and apparatus for automatically mounting components onto a circuit board.
An example of the construction of a prior art generic electronic component mounting apparatus is shown in FIG. 7, and a flowchart of its operation control sequence is shown in FIG. 8. With reference to these FIGS. 7 and 8, a prior art electronic component mounting method will be described.
As shown in FIG. 9, a plurality of mounting patterns 2a, 2b, 2c, etc. and target marks 3a, 3b, 3c, etc. are formed on a circuit board 1, and the production of the circuit board is performed by mounting a desired electronic component on the mounting patterns 2a, 2b, 2c, etc. In this case, the target marks 3a, 3b, 3c, etc. are used for correcting the mounting positions which delicately vary on every circuit board 1 depending on a contraction of the circuit board occurring in calcining the mounting patterns 2 on the circuit board 1, and depending on the state in which the circuit board 1 is supported by a circuit board positioning device 4.
The production of the circuit board by means of the electronic component mounting apparatus is performed firstly by forming mounting data from the mounting pattern of the circuit board 1 to be produced (Step #1). FIG. 10 shows an example of the mounting data. Further, a positional relation between the mounting patterns and the target marks of the circuit board for reference use is detected and mark data is formed (Step #2). FIG. 11 shows an example of the mark data.
According to these various data, a specified number of circuit boards are produced. A production procedure is to firstly bring the circuit board 1 from a board conveyance section 5 into a circuit board positioning device 4 (Step #3). Next, a board image pickup device 6 is aligned in position with the desired target mark 3a, 3b, 3c, etc. of the circuit board 1 from above to pick up the image of the target mark 3a, 3b, 3c, etc. and the target mark position of the circuit board 1 is detected. According to this image pickup result, the mounting position and the angle are corrected (Step #4).
Subsequently, the electronic component mounting head 7 is moved onto a component supply device 8 (component supply units 8a or 8b) by an XY robot 20 including an X-direction driving unit 20x for moving the head 7 in an X direction and two Y-direction driving units 20y for moving the X-direction driving unit 20x and the head 7 in a Y direction perpendicular to the X direction. Then, a suction nozzle 9 of the head 7 is positioned in a component supply position, and the desired electronic component corresponding to the mounting data is sucked (Step #5). In this case, the vertical and rotative movements of the suction nozzle 9 in the electronic component mounting head 7 are achieved by a mechanism as shown in FIG. 12, where the suction nozzle 9 moves vertically while being interlocked with a shaft 10 and the vertical movement is effected with an actuator 11 used as a drive source. In this stage, a locus of the shaft 10 when it moves vertically is regulated by a nut 12 and a nut 13. Further, the suction nozzle 9 rotates while being interlocked with the shaft 10, and its rotative movement is effected with an actuator 15 used as a drive source via a belt 14.
Next, the electronic component mounting head 7 is moved so that the sucked electronic component is positioned above a component image pickup device 16, and the suction posture of the electronic component sucked by the suction nozzle 9 is detected by the component image pickup device 16. Based on this image pickup result, the final mounting position and angle of the electronic component are determined (Step #6).
Finally, by positioning the electronic component mounting head 7 so that the electronic component is positioned in the obtained mounting position on the circuit board and moving the suction nozzle 9 downward, the mounting of the electronic component is performed (Step #7).
Thus one circuit board is produced by repetitively performing such a series of sucking and mounting operations according to the preparatorily formed mounting data, and it is determined whether or not the production of the circuit board has been completed at this point of time (Step #8). When the production has been completed, the circuit board is brought out of the circuit board positioning device 4 to the board conveyance section 5 (Step #9). When the production has not been completed, the sucking and mounting operations of the next electronic component will be achieved (Steps #5 through #7).
However, the shaft 10 has a bending attributed to the processing accuracy as shown in FIG. 13. Accordingly, a displacement of average 5-10 .mu.m (increasing toward the nozzle tip in relation to the nut 13) occurs when the shaft 10 is moved vertically by the actuator 11. The suction posture of the electronic component is detected by the component image pickup device 16, and the suction to nozzle 9 is moved down for the mounting of the electronic component in the mounting position on which the image pickup result is reflected. Therefore, the displacement of average 5--10 .mu.m occurs at the nozzle tip and this causes a problem in that the electronic component cannot be mounted in the desired mounting position. 10% or more of all recognition errors might be due to the displacement.
In this case, it can be considered to make the component recognition height equal to the mounting height for the purpose of preventing the displacement of the nozzle tip. In this case, it is required to first move the suction nozzle 9 up after recognizing the component, and thereafter move the nozzle down for the achievement of mounting. Therefore, a worthless vertical movement of the suction nozzle 9 occurs, thereby reducing productivity. Then, in order to eliminate the worthless vertical movement of the suction nozzle 9, the mounting height is generally set below the component recognition height so that the suction nozzle 9 can be moved down from the recognition height after the recognition of the component directly to the mounting height for the achievement of the mounting of the electronic component.
Further, when a rotative deviation occurs through the detection of the suction posture of the electronic component by the component image pickup device 16, the shaft 10 is to be rotated by the actuator 15 to correct the deviation. In this stage, as shown in FIG. 14, a rotative displacement attributed to the bending of the shaft 10 occurs at the suction nozzle tip, and therefore, a further displacement occurs.